Incorrect matches is

Options

A. `COCl_(2)` -phosgene
B. `SO_(2)Cl_(2)`- Thionyl chloride
C. `ClCH_(2)CH_(2)SCH_(2)CH_(2)Cl` - mustard gas
D. `H_(2)SO_(5)` - Caro's acid

Answer

To solve the question regarding incorrect matches, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the first option: CoCl2**
- CoCl2 is known as cobalt(II) chloride.
- This statement is correct as CoCl2 is indeed cobalt(II) chloride.

2. **Identify the second option: SO2Cl2**
- The question states that SO2Cl2 is thionyl chloride.
- However, thionyl chloride has the chemical formula SOCl2, not SO2Cl2.
- Therefore, this statement is incorrect.

3. **Identify the third option: ClCH2CH2SCH2CH2Cl**
- This structure represents mustard gas, which is also known as sulfur mustard.
- The formula ClCH2CH2SCH2CH2Cl is indeed the correct representation of mustard gas.
- Thus, this statement is correct.

4. **Identify the fourth option: H2SO5**
- H2SO5 is known as peroxymonosulfuric acid or Caro's acid.
- This statement is also correct.

### Conclusion:
After analyzing all the options, we find that the incorrect match is in option 2, where SO2Cl2 is incorrectly stated to be thionyl chloride. The correct formula for thionyl chloride is SOCl2.

### Final Answer:
The incorrect match is option 2: SO2Cl2 is not thionyl chloride.

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